2-Propanol is an important intermediate in organic synthesis and is an important solvent in industry. It has a wide range of applications, and some applications require high-purity 2-propanol.
One of the processes for producing 2-propanol is a reaction of acetone with hydrogen. In the production of high-purity 2-propanol, the 2-propanol from the reaction is generally purified by distillation. The distillation, however, involves large amounts of energy.
Allowable kinds and amounts of impurities vary depending on the use applications. In some uses, distillation often cannot provide 2-propanol of high purity with sufficient level of impurity removal.
Accordingly, reducing impurities that are by-produced in the reaction for 2-propanol is an effective approach for the production of 2-propanol having high purity.
Processes are established for the production of 2-propanol by reducing acetone with hydrogen. For example, Kogyo Kagaku Zasshi (Industrial Chemical Magazine), Vol. 54, Book 1, p. 27 (1951) (Nonpatent Document 1) describes a process of producing 2-propanol by hydrogenating acetone in the presence of a Raney nickel prepared from Ni/Al (1:1) alloy by a common method.
The yield of 2-propanol described in Nonpatent Document 1 is 93.3%. A higher yield is necessary in consideration of industrial production of 2-propanol.
In the established processes, increasing the acetone conversion to improve the yield of 2-propanol also increases the amounts of by-products such as diisopropyl ether, propane, ethane and methane, causing problems in the separation of 2-propanol from the reaction mixture.
Nonpatent Document 1 teaches that the addition of water accelerates the hydrogenation and the yield of 2-propanol is increased to 98.7%. When this teaching to increase the 2-propanol yield is practiced in the industrial production of 2-propanol by hydrogenating acetone, the reaction mixture will contain 30% of water and large amounts of energy are required to separate 2-propanol therefrom, causing increased costs and economic problems.
JP-A-S62-012729 (Patent Document 1) describes that impurities are reduced by addition of water in the hydrogenation of acetone. The amount of water is defined as water content in the reaction system. However, the working example and comparative examples in this patent document substantially disclose a water content in the reaction system of 0.3 wt % alone. Further, the process according to Patent Document 1 requires that at least 0.5 wt % of acetone should remain unreacted. The reaction efficiency should therefore be improved.
JP-A-2001-039910 (Patent Document 2) describes that impurities are reduced by adding water to acetone. In detail, Patent Document 2 discloses that acetone having a very small water content is hydrogenated. In more detail, the patent document describes that acetone with a water content of not more than 1.0% by mass is hydrogenated to isopropanol. The working examples in Patent Document 2 do not disclose any water contents.    Patent Document 1: JP-A-S62-012729    Patent Document 2: JP-A-2001-039910    Nonpatent Document 1: Kogyo Kagaku Zasshi (Industrial Chemical Magazine), Vol. 54, Book 1, p. 27 (1951)